Re: Narrow filter for CW #ubitxcw


Jerry Gaffke
 

Looks like PA1FOX has successfully added a second crystal filter for CW:
    https://groups.io/g/BITX20/message/48555
Perhaps Farhan has done this as well.

A perhaps easier hack is to simply add an audio filter for CW, as many here have done.
Some operators will prefer the narrow crystal filter for CW, as this avoids overloading
the receiver audio pre-amp when a strong nearby signal is present.

Evan's hack:  https://groups.io/g/BITX20/message/71042
is well worth trying.  I have not tried the KD8CEC firmware, but should be possible
to implement this with a firmware change only, no Nextion display, no hardware mods.

Jerry, KE7ER


On Mon, Aug 12, 2019 at 06:10 PM, Ashhar Farhan wrote:
The ubitx has an option for narrow band filter. There are pins to install it. The way it works is a bit of a hack :
1. The CW filter is at a different frequency. Let's imagine it is at 4.915 MHz. It is installed parallel to the 11.059 MHz SSB filter.
2. When choosing CW filter, you have to switch the second conversion oscillator from 56.059 Mhz (45 + 11.059) to 49.915 Mhz (45 +4.915). Shift the BFO to 4.914500 (According to your taste of CW tone).
Apart from designing the crystal filter, this hack is mostly about software changes.
 

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